Sized polyolefin yarn



United States Patent 3,228,791 SiZEl) POLYOLEFIN YARN Walter B. Armour, Plainfield, N.J., Michael P. Diamantepoulos, South Acton, Mass, and Herbert C. Olsen, Berkeley Heights, N.J., assignors to National Starch and Chemical Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 26, 1962, Ser. No. 233,439 3 Claims. (Cl. 117138.8)

This invention relates to a method for the sizing of polyolefin yarns and filaments and to the materials thus sized. More specifically, it relates to the sizing of polyolefin yarns and filaments with compositions which provide these materials with improved tensile strength, compactness, smoothness, and resistance to abrasion.

The sizing of yarns and filaments consists of the coating or impregnation of said yarns and filaments with a suitable sizing agent which may be inthe form of either a lacquer or an aqueous solution or dispersion. This sizing operation is necessary in order to substantially strengthen the yarns and filaments so as to enable them to withstand subsequent processing operations. Aqueous dispersions of starch and starch derivatives have generally been utilized to size cotton and other natural fibers. The use of such starch-based dispersions, however, has not been applicable to the sizing of synthetic fibers and filaments. Thus, the use of starches and their derivatives for the sizing of synthetic fibers and filaments is effectively limited by the stability and viscosity variations of their dispersions and also by their rather limited affinity for the material to which they are being applied. The inadequacies of these starch-based dispersions have therefore led to the use of expensive and only partly effective polymeric materials, such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, and the like, as sizing agents for synthetic fibers and filaments.

The improved properties of the recently developed yarns and filaments based on polypropylene and other polyolefins, such as polyethylene, have made it highly desirable to attempt to use these yarns and filaments in an increasing variety of applications in the textile field. Thus, it has been found that polypropylene yarns and filaments possess relatively low specific gravity and consequently provide a light weight material of high covering ability. Moreover, these polypropylene materials possess highly satisfactory properties of strength and smoothness. Despite the enhanced properties of polypropylene yarns and filaments the extent of their use has been somewhat curtailed due to the lack of a satisfactory sizing agent for the polypropylene. Similarly, other polyolefin yarns and filaments have not been employed because of the dearth of satisfactory sizing agents.

It is an object of this invention to provide a method for the sizing of polypropylene and other polyolefin yarns and filaments. It is a further object of this invention to provide a novel sizing composition for polypropylene and other polyolefin yarns and filaments which imparts thereto improved properties of strength and resistance to abrasion. Other objects and the advantages of this invention will be apparent from the discussion that appears hereinafter.

For the purposes of this invention, reference will be made hereinafter only to treatment of polypropylene yarns and filaments. It should be noted that such reference is not intended to restrict the application of our invention, but is merely made in light of the greater extent of textile usage which polypropylene currently enjoys, as compared to other polyolefins. Therefore, it is to be understood that whenever reference is hereinafter made to polypropylene, such reference also comprehends the use of other polyolefinic materials, including mixtures of polyolefins as well as copolymers of olefins with ethylenically unsaturated comonomers.

In accordance with the invention, polypropylene yarns or filaments are sized with a novel chlorinated polymer mixture which is prepared from a mixture of atactic polypropylene and an ethylene:propylene copolymer. The polyolefin materials thus treated with this polymer mixture have been found to display characteristics of enhanced tensile strength, compactness, smoothness, and resistance to abrasion.

The chlorinated polymers mixtures which are used as the sizing agents in the process of this invention are prepared by blending atactic polypropylene and ethylene: propylene copolymers in the form of an organic solvent solution which is then chlorinated in the presence of a suitable free radical initiator. The sizing compositions of our invention are, in effect, chlorinated polymeric compositions wherein the two components from which they are derived, viz., the atactic polypropylene and the ethylenezpropylene copolymer, are chemically bonded to one another.

In preparing the sizing agents of our invention, separate solutions of atactic polypropylene and of an ethylenezpropylene copolymer are blended and thereafter subjected to a chlorination procedure in the presence of a free radical catalyst or initiator. The chlorine may be introduced by bubbling chlorine gas directly into the reaction mixture or by refluxing the latter in the presence of sulfuryl chloride, or by any of the conventional chlorination methods, such as treatment with thionyl chloride or treatment with phosphorous pentachloride. The free radical initiators or catalysts are usually solvent soluble organic peroxides sugh as benzoyl or lauroyl peroxide.

The chlorinated polymer mixtures used are prepared, for example, as follows: Organic solvent solutions of the atactic polypropylene and of the ethylene:propylene copolymer are first prepared with the process of solution being assisted by refluxing and agitation of the mixture. The resulting solutions are then agitated and heated to reflux. While the thus prepared solutions are being maintained at constant reflux, the free radical catalyst is added and soon dissolved in the mixture. Sulfuryl chloride is then slowly added. The mixtures are maintained at reflux for periods of time ranging from 5 to 10 hours, thereby yielding the chlorinated polymer mixture compositions used in our invention. Additional details relating to the preparation of our chlorinated polymer mixtures are set forth in a copending patent application entitled Polyolefin Polymer Mixtures, Serial No. 214,519, filed August 3, 1962, and assigned to the assignee of the subject application.

For use as a sizing agent in the process of this invention, the chlorinated polymer mixtures may contain from about 5% to about 35%, by weight, of chlorine. The polymer mixture should also have a ratio of atactic polypropylene to the ethylenezpropylene copolymer ranging from 30:70 to :30. Moreover, the ethylene: propylene copolymers used to prepare the polymer mixture should have a Mooney viscosity ranging from 20 to and a ratio of ethylenezpropylene ranging from 35:65 to 70:30, by weight. The free radical initiator or catalyst is employed in a concentration of from 0.1% to 1.0% by weight as based on the total weight of the polymer blend which is being reacted.

For the purposes of this invention, whenever we use the term polypropylene yarn, it is to be understood that said reference is equally applicable to the use of polypropylene filaments. Thus, the sizing compositions of our invention may be applied to polypropylene filaments as well as to yarns wherein the polyolefin filament may be only one component of the composite yarn.

The chlorinated polymer mixtures of our invention may be applied to polypropylene yarns in the form of the organic solvent solutions wherein they were prepared or in the form of an aqueous emulsion. The polymer mixture lacquers may be readily emulsified by adding an aqueous solution of an emulsifier, such as polyvinyl alcohol, morpholine-oleic acid mixtures, and the like, to the lacquer while the lacquer is vigorously agitated. Any of the conventional means generally used by the practitioner for the sizing of yarns may be employed in our process. Thus, for example, the polypropylene yarn may be passed through a bath comprising an aqueous emulsion of our sizing composition, then through a set of squeeze rolls in order to remove excess size, and finally, through a drying chamber or over the surface of internally heated drying cylinders called cans. For most purposes, our chlorinated polymer mixtures should be applied to polypropylene yarns in a concentration ranging from about 1% to about of resin solids as based on the weight of dry yarn. The resin solids content of the sizing compositions may vary considerably depending upon a number of factors, including the number of filaments in each yarn, the construction of the fabric into which the yarn 4 EXAMPLES The following examples illustrate the sizing of polypropylene yarn using the novel sizing compositions of our invention.

Several chlorinated polymer mixture lacquers, which are described in the table below, were prepared by means of the procedure described previously. These lacquers were then converted into aqueous emulsions by adding an aqueous solution of an emulsifier to the lacquer with vigorous agitation. These emulsions were then used to size polypropylene yarns by means of a process wherein the yarns were passed through a bath containing the emulsion. The wet yarns were then passed through a set of squeeze rolls to remove excess sizing composition, and were thereafter dried on heated cans maintained at a temperature of about 200 F.

The polypropylene yarn sized according to the method set forth above was then tested in order to determine its strength characteristics. In testing the yarn, an instrument known as the Duplan cohesion tester was utilized. This device consists of a mechanically propelled friction plate which moves back and forth over the sample of sized yarn while the latter is tightly laced between a series of porcelain hooks. Upon noticing a partial separation or fraying of the yarn, note is made of the number of cycles which have elapsed. The separation of the yarn, in this manner, indicates that the protective action of the size has been lost. Thus, the number of cycles which each sample withstands is a direct indication of the sizing efiiciency of the particular sizing composition used.

The compositions of the sizing formulations used as well as the results of the cohesion strength tests thereof are set forth in the following table.

Composition Polymer of Mixture Ethylene: Propylene Copolymer Parts of Parts of Parts of Percent No. of

Atactic Methy- Carbon Chlorine Abrasion Polymer Mixture No. Polyprolene Tetrain Cycles Mooney Ethylene: pylene Chloride chloride Ploymer Withstood Parts viscosity propylene Mixture Ratio is to be woven, loom speeds, and similar variables related to the sizing and weaving processes.

The polymer mixtures of our invention may be used as the sole sizing agent for polypropylene yarns or, if desired, they may also be formulated with other sizing agents. In general, our chlorinated polymer mixtures are used as the sole sizing agents in those cases where they are to be applied to polypropylene filaments. However, when polypropylene yarns are to be sized, these polymer mixtures may also be formulated with conventional sizing agents, such as starches, polyvinyl alcohol, polyacrylic acid, and the like. In the latter instances, about 10% to about 20% of the polymer mixture is used, as based on the total weight of the sizing composition which is employed.

Various additives, e.g., oils and lubricants, may also be incorporated in the sizing compositions of our invention. It should be noted, however, that the characteristics of our polymer mixtures make the inclusion of such additives unnecessary in order to achieve satisfactory s ze y rn In the following examples, which further illustrate the embodiment of our invention, all parts given are by weight unless otherwise indicated.

The number of abrasion cycles withstood by the yarn sized with our polymer mixture formulations was considerably higher than the number withstood by yarn sized with conventional sizes. By contrast, the maximum number of cycles withstood by polypropylene yarn sized with polyacrylic acid, polyvinyl alcohol, and the like usually were no more than about 20 cycles. It can thus be seen that the use of our sizing formulations offers significant advantages over the sizes previously employed.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the invention as defined by the following claims.

We claim:

1. A polyolefin yarn sized with a composition consisting essentially of a chlorinated polymer mixture of atactic polypropylene and an ethylene:propylene copolymer; wherein the amount of chlorine in the polymer mixture ranges from 5% to 35%, by weight of the polymer mixture; wherein said ethylene:propylene copolymer has a Mooney viscosity ranging from 20 to and an ethylenezpropylene ratio ranging from 35:65 to 70:30; and wherein the ratio of atactic polypropylene to ethylenezpropylene copolymer ranges from 30 .70 t9 70:30.

2. A polypropylene yarn sized with a composition consisting essentially of a chlorinated polymer mixture of atactic polypropylene and an ethylenezpropylene copolymer; wherein the amount of chlorine in the polymer mixture ranges from 5% to 35%, by weight of the polymer mixture; wherein said ethylenerpropylene copolymer has a Mooney viscosity ranging from to 90 and an ethylene1propylene ratio ranging from 35:65 to 70:30; and wherein the ratio of atactic polypropylene to ethylenezpropylene copolymer ranges from :70 to 70:30.

3. A polyolefin yarn sized with a composition consisting essentially of a chlorinated polymer mixture prepared by chlorinating an organic solvent solution of a mixture of atactic polypropylene and an ethylene:propylene copolymer, said chlorination being conducted in the presence of a free radical catalyst; wherein the amount of chlorine in the polymer mixture ranges from 5% to by weight of the polymer mixture; wherein said ethylenerpropylene copolymer has a Mooney viscosity ranging from 20 to 90 and an ethylenezpropylene ratio ranging from 35:65 to :30; and wherein the ratio of atactic polypropylene to ethylenezpropylene copolymer ranges from 30:70 to 70:30.

References Cited by the Examiner UNITED STATES PATENTS 2,748,105 5/1956 Becker et al. 290--96 X 2,854,357 9/1958 Johnson et a1. 117--139.5 X 2,909,447 10/1959 Scott 117-1395 2,927,047 3/ 1960 Schulde et a1. 117--138 2,968,637 1/1961 Bowers 260-29.6 3,000,867 9/1961 Fisher 26088.2 3,008,215 11/1961 Pitts 117-139.5 X 3,062,795 11/ 1962 Cain et a1. 260-96 X 3,125,462 3/ 1964 Rachinsky 117-139.5 3,126,297 3/1964 Diamantopoulis et a1.

20 WILLIAM D. MARTIN, Primary Examiner.

R. HUSACK, Assistant Examiner. 

1. A POLYOLEFIN YARN SIZED WITH A COMOSIION CONSISTING ESSENTIALLY OF A CHLORINATED POLYMER MIXTURE OF ATACTIC POLYPROPYLENE AND AN ETHYLENE:PROPYLENE COPOLYMER; WHEREIN THE AMOUNT OF CHLORINE I THE POLYMER MIXTURE RANGES FROM 5% TO 35%, BY WEIGHT OF THE POLYMER MIXTURE; WHEREIN SAID ETHYLENE: PROPYLENE COPOLYMER HAS A MOONEY VISCOSITY RANGING FROM 20 TO 90 AND AN ETHYLENE:PROPYLENE RATIO RANGING FROM 35:65 TO 70:30; AND WHEREIN THE RATIO OF ATACTIC POLYPROPYLENE TO ETHYLENE: PROPYLENE COPOLYMER RANGES FROM 30:70 TO 70:30. 